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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.5 (Degradation: Biochemical Oxygen Demand)
Principles of method if other than guideline:
Development of a BOD test for large volume experiments and quiescent conditions such as would be found in the environment (e.g. lake). System developed for determination of the rate, degree and extent of biodegradation of organic chemicals. Oxygen consumption, TOC, DOC and bacterial growth were determined during the test.
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: St. Louis Metropolitan Sewer District manhole, Washington University campus
- Preparation of inoculum for exposure: raw wastewater was settled and filtrated
Duration of test (contact time):
20 d
Initial conc.:
10 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Parameter followed for biodegradation estimation:
DOC removal
Parameter followed for biodegradation estimation:
TOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: according to Standard Methods (for BOD testing) for the examination of Water and Wastewater (Am. Pub. Health Assn., New York 1965)
- Test temperature: 19.5 - 20.5 °C
- pH: not specified
- Inoculum: 2 mL/L settled, raw wastewater

TEST SYSTEM
- Culturing apparatus: BOD apparatus of Orford et al. 1953 . Two autoclaved 9 L pyrex bottles with a connecting siphon. The one bottle was placed lower than the other in order to allow atomatic flow of the medium from the higher bottle to the lower one, at sampling time points. The lower bottle was kept full and closed in order to avoid air while the higher bottle was opened.
- Number of culture flasks/concentration: 1
- Method used to create aerobic conditions: if reaeration was necessary, filtered air was blown for 20-30 min directly into the lower bottle
- Measuring equipment: see details on analytical methods for more detail

SAMPLING
- Sampling frequency: on days 0, 1, 2, 3, 4, 5, 7, 9, 12, 16 and 20
- Sampling method: samples were taken from the lower bottle by opening the hose clamp of the siphon. The volume of the sample was replaced continuously through the siphon from the second bottle, which was covered but had access to the atmosphere. The first 50 mL were descarde in order to clear the sampling channel. Samples for dissolved oxygen: 125 mL in a reagent bottle; for COD and TOC analysis: 30 to 40 mL in a clean tube; for centrifugation: 40 mL (also for TOC analysis); nitrite determination: 50 mL in a nessler tube.

CONTROL AND BLANK SYSTEM
- Inoculum blank: included (no carbon source)
- Abiotic sterile control: not included
- Toxicity control: not included
- Reference substance: glucose and glutamic acid
Reference substance:
other: glucose-glutamic acid solution, 10 mg/L
Preliminary study:
no data
Parameter:
% degradation (O2 consumption)
Value:
89
Sampling time:
5 d
Remarks on result:
other: BOD5 = 0.16 mg/mg
Parameter:
% degradation (O2 consumption)
Value:
89
Sampling time:
20 d
Remarks on result:
other: BOD20 = 0.16 mg/mg
Details on results:
TOC and COD data confirmed the data from the oxygen consumption.
Parameter:
BOD5
Value:
0.16 g O2/g test mat.
Parameter:
BOD5
Value:
89 other: % of TOD
Results with reference substance:
The reference with glucose-glutamic acid solution (10 mg/L) showed immediate uptake of oxygen at the start of the test. A maximum uptake was observed the fifth day. After this timepoint no further O2 uptake was observed. The 5 -day BOD was 1.49 mg/mg. COD and TOC analysis verified the depletion of the substrate.
Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to the analogue justification provided in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Parameter:
% degradation (O2 consumption)
Value:
89
Sampling time:
5 d
Remarks on result:
other: Source: Young et al., 1968
Parameter:
% degradation (O2 consumption)
Value:
89
Sampling time:
20 d
Remarks on result:
other: Source: Young et al., 1968
Parameter:
% degradation (O2 consumption)
Value:
53.6
Sampling time:
5 d
Remarks on result:
other: at 20 °C
Remarks:
Source: Deshkar et al., 1985
Parameter:
% degradation (O2 consumption)
Value:
91.8
Sampling time:
5 d
Remarks on result:
other: at 25 °C
Remarks:
Source: Deshkar et al., 1985
Parameter:
% degradation (O2 consumption)
Value:
94.6
Sampling time:
5 d
Remarks on result:
other: at 35 °C
Remarks:
Source: Deshkar et al., 1985

Additional to the above listed degradation results, Hongwei et al., 2003 found the read across substance oxalic acid to be rapidly biodegradable under anaerobic conditions without providing an exact value. The study was performed according to international standards and the result was based on data from the pressure of total gas produced during biodegradation, the chemical oxygen demand and the determination of the microbial activity by measuring INT-Dehydrogenase activity.

Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Qualifier:
equivalent or similar to guideline
Guideline:
other:
Version / remarks:
according to Standard Methods for the examination of water and wastewater, 15th ed. APHA, AWWA & WPCF, NY, 1980
Deviations:
not specified
Principles of method if other than guideline:
BOD5 was determined at three different temperatures, 20, 25 and 35 °C. The test was performed according to Standard Methods for the examination of water and wastewater, 15th ed. APHA, AWWA & WPCF, NY, 1980 as mentioned by the authors
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
No details provided
Duration of test (contact time):
5 d
Initial conc.:
2 g/L
Based on:
test mat.
Initial conc.:
264 mg/L
Based on:
COD
Parameter followed for biodegradation estimation:
other: dissolved oxygen
Details on study design:
TEST CONDITIONS
- Test temperature: 20, 25 and 35 °C
- pH: 7
- pH adjusted: yes


Preliminary study:
not specified
Parameter:
other: dissolved oxygen
Value:
53.6
Sampling time:
5 d
Remarks on result:
other: at 20 °C
Parameter:
other: dissolved oxygen
Value:
91.8
Sampling time:
5 d
Remarks on result:
other: at 25 °C
Parameter:
other: dissolved oxygen
Value:
94.6
Sampling time:
5 d
Remarks on result:
other: at 35 °C
Parameter:
BOD5
Value:
53.6 other: % BOD of COD
Remarks on result:
other: after 5 d at 20 °C
Parameter:
BOD5
Value:
91.8 other: % BOD of COD
Remarks on result:
other: after 5 d at 25 °C
Parameter:
BOD5
Value:
94.6 other: % BOD of COD
Remarks on result:
other: after 5 d at 35 °C

Table 1: Progressive BOD (exp. values).

20 °C 25°C  35°C
Day  Progressive BOD (exp. value) BOD per day (% of COD) Progressive BOD (exp. value) BOD per day (% of COD) Progressive BOD (exp. value) BOD per day (% of COD)
1 10 3.7 35 13.2 46 17.4
2 30 7.6 154 45 187 53.4
3 60 11.4 201 20 224 14
4 130 26.5 210 3.4 225 0.37
5 145 5.6 240 11.3  -  -
Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
according to guideline
Guideline:
ISO 11734 Water quality - Evaluation of the "ultimate" anaerobic biodegradability of organic compounds in digested sludge - Method by measurement of the biogas production
Version / remarks:
1995
GLP compliance:
not specified
Oxygen conditions:
anaerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: wastewater treatment plant in Beijing
- Preparation of inoculum for exposure: 50 mL anaerobic sludge was centrifuged at 1000 x g and poured into the 600 mL serum bottle
- Pretreatment: cultured at 35 °C for ca. 1 week in order to reduce the residual organic substrate in the sludge
Duration of test (contact time):
50 d
Initial conc.:
100 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
other: the pressure of total gas produced in biodegradation was measured
Parameter followed for biodegradation estimation:
other: COD
Parameter followed for biodegradation estimation:
other: determination of microbial activity by measuring INT-Dehydrogenase activity
Remarks:
according to (Hongwei et al., 2002)
Details on study design:
TEST CONDITIONS
- Composition of medium: according to ISO 11734
- Test temperature: 35 ± 1 °C
- pH: 7 ± 0.2 (with sodium bicarbonate)
- pH adjusted: yes

TEST SYSTEM
- Culturing apparatus: serum bottles
- Method used to create anaerobic conditions: medium purged with N2 for 5 min and then sealed in order to remove residual oxygen

CONTROL AND BLANK SYSTEM
- Inoculum blank: included


Remarks on result:
other: for result refer to field `details on results´
Details on results:
In this study the anaerobic biodegradability of 47 aliphatic compounds was tested in order to develop on the basis of these data a quantitative structure biodegradability relationship (QSBR). Oxalic acid was among these substances and was found by the authors to be readily biodegradable under anaerobic conditions. This result is based on the value of the integrated assessment index (>1) as described under `any other information on materials and methods incl. tables´. Further details on the results of oxalic acid are not included. However, the results for the various groups of substances are consistent among each other.
Validity criteria fulfilled:
not specified
Interpretation of results:
other: readily biodegradable under anaerobic conditions

Description of key information

Dipotassium oxalate anhydrate (CAS 583-52-8) is readily biodegradable based on read across data from CAS 144-62-7

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Data on the biodegradability of dipotassium oxalate anhydrate (CAS 583-52-8) were not available. Therefore, a read across was performed to the analogue substance oxalic acid (CAS 144-62-7). Three publications are available on the biodegradability of oxalic acid.

In the study by Young et al. (1968) the ready biodegradability of oxalic acid was tested with a method similar to EU Guidance C.5. Non-adapted, activated sludge from a domestic sewage treatment plant was used as inoculum and was exposed to an initial nominal test substance concentration of 10 mg/L. After 5 and 20 d test duration, 89% degradation of the test substance was observed.  

Similar observations were made by Deshkar et al. (1985). Non-adapted domestic sewage sludge was exposed for 5 d at three different temperatures (20, 25 and 35°C) to 2 g/L test material (264 mg/L COD). The procedure of the study was similar to the “Standard Methods for the examination of water and wastewater 15th ed. APHA, AWWA & WPCF, NY, 1980”. The authors reported 53.6, 91.8 and 94.6% biodegradation at 20, 25 and 35°C, respectively. 

Furthermore, Hongwei et al. (2003) tested the anaerobic biodegradation of oxalic acid according to the ISO guideline 11734. Non-adapted domestic sewage sludge was exposed to 100 mg/L (TOC) of the test substance for 50 d under anaerobic conditions. Three assessment indices named CI, GI and AI were calculated by the authors. These indices were associating to the changes of the experimental data of COD, gas volume and INT-DHA, respectively. Subsequently the integrated assessment index (IAI), which was based on CI, GI and AI, was calculated. The statement of the ready biodegradability of the substances in this publication was based on the value of the IAI (if IAI>1, substance could be assumed readily biodegradable). On this basis the authors found that oxalic acid was readily biodegradable under tested conditions.

All available data indicate that oxalic acid (CAS 144-62-7) is rapidly biodegradable. On the basis of the read across data on oxalic acid, the target substance dipotassium oxalate anhydrate (CAS 583-52-8) is considered rapidly biodegradable as well. The target substance is very well soluble in water and will dissociate into its salts, oxalic acid, which is well biodegradable, and potassium ions, which are not further taken into account for biodegradability since it is an inorganic substance.